Fluted or corrugated panels have a wide range of applications. They are generally used as an economical alternative to solid sheet panels, as they have an extraordinary strength to weight ratio, with much greater insulating properties than solid sheet panelsxe2x80x94that is if the ends of the fluted panels are closed. The fluted panels, which can be extruded from high-density polypropylene or polyethylene are more durable than corrugated fiberboard, lighter than wood, and impervious to water and can withstand harsh chemicals. For instance, fluted thermoplastic panels can be used to form reusable containers and boxes, displays, screen printings, automotive interior components, storage cabinets, walls, supports, etc. Transparent fluted panels also can be used as skylights, wall dividers, etc.
Such a fluted panel typically comprises a pair of spaced apart thermoplastic layers or skins interconnected with longitudinally extending ribs or flutes that form longitudinally extending interior passageways, as illustrated in U.S. Pat. No. 5,658,644, the disclosure of which is incorporated herein by reference. The flutes are uniformly spaced apart and run in one direction for the entire length or width thereof. The flutes, however, can run in any direction and can be angled. The cross section of the panel having perpendicular flutes looks like a series of side-by-side square tubes having open ends, which will allow air, liquid or any material to flow freely inside the length of the panel. Such fluted panels are commercially available from INTEPLAST GROUP, LTD of Livingston, N.J. (sold under the name of IntePro(copyright), as advertises at http://www.worldpak.com) and COROPLAST, INC. of Dallas, Tex. (sold under the name of Coroplast(trademark), as advertises at http://www.coroplast.com). These companies manufacture thermoplastic panels in various sizes and thickness, ranging from 2 mm to 13 mm, with the skin thickness ranging from 6.5 mil to 36 mil and the flute thickness ranging from 6.5 mil to 29 mil. These panels, however, come with open ends (at four sides for square or rectangular shape), which limit their use.
The problem with open ends is that they allow dirt and water to collect inside. Moreover, the open edges can be sharp, making it unsuitable for consumer use, as the sharp edges can catch and scratch skin and clothing. Further, the open edges can be unsightly, making it esthetically undesirable. Thus, it would be desirable to close the open ends. Indeed, properly closing and sealing the ends and making them more esthetically appealing would greatly extend the use of such panels. The insulating and inert (non-reactive) properties of sealed thermoplastic panels are highly desirable qualities. Because the extruded polypropylene is highly non-reactive, it is qualified for medical use, which makes the panels an excellent candidate for food, pharmaceutical, medical storage, and packaging applications. Presently these thermoplastic panels have limited uses, as there is not an economical solution for sealing and finishing the edges. Other markets that could benefit from the fluted panels if the edges are sealed are, for example, storage, cabinetry, casework, and furniture industries.
Currently there are two methods of finishing or sealing the ends of extruded plastic materials. The first finishing method is covering the open ends with either an unlike or like material. This first method involves fitting the panels in U-shaped channels. An example of this is the current method for finishing skylights and divider panels, where the open ends are capped with U-shaped channels of like material. This method is labor intensive and may need to rely on bonding agents to securely attach the channels. The bonding alternative is not only expensive, it requires a long curing period, and the result is not all that esthetically pleasing.
The second method involves heating and stamping the flat sheets at the portion of the skins that overlap with a die to press and fuse them together. This method seals the edges together very well. But the tooling required to make the die is very expensive and limited to a single shape. This method makes shorter productions unpractical. This method is also not suited for producing esthetically pleasing ends for consumer products because the resulting ends are fairly sharp, which can scratch skin and clothing.
Accordingly, there is a need for an economical solution for producing an esthetically pleasing end in the current fluted panels. The present invention addresses this need.
The present invention relates to a method and an apparatus for closing an open end of a product, and the product formed thereby. The product, which can be a panel, such as a fluted thermoplastic panel, including those made of polypropylene, polyethylene, polycarbonate, etc., has a first layer with a first end and a second layer with a second end. The first layer is spaced apart from the second layer and the first and second ends define an open end of the product. The first and second layers are heat sealable, weldable, or fusable.
The method comprises the step of rolling at least the first layer toward the second layer and contacting the first layer with the second layer, and fusing the first and second layers by heating at least one of a portion of the first layer that contacts the second layer and a portion of the second layer that contacts the first layer. The rolling step can include overlapping the first layer over the second layer or contacting an edge of the first layer to an edge of the second layer.
The rolling step also can include rolling both the first and second layers so that edges of the first and second layers contact each other, or the edges can be made to abut each other, or so that the first layer overlaps and contacts the second layer.
The fusing step can include heating both portions of the first and second layers that contact each other, and both portions can be simultaneously heated.
The present method also can include a step of trimming at least the second layer so that the first layer extends beyond the second layer to form a tab. The tab can be dimensioned to overlap the second layer. The first and second layers can also be trimmed so that the first and second layers extend substantially equally.
The present method also can include a step of pressing and cooling the fused layers.
The apparatus can include a pair of first and second guides, and a heater. The first and second guides can be configured to contact and guide at least the first layer and cause the first layer to contact the second layer, while one of the first and second guides and the product is moved relative to the other of the first and second guides and the product. The heater can heat one or both of the guides to heat and melt at least one of a contact portion of the first layer that contacts the second layer and a contact portion of the second layer that contacts the first layer, so that the contact portions fuse upon contact.
In one embodiment, the first and second guides can be configured to contact and guide the first layer to cause the first layer to overlap the second layer. In this respect, the heater can be configured to heat only the first guide, and the first guide can be configured to simultaneously heat both contact portions of the first and second layers that are fused. The first guide can comprise a body having a first guide surface and a second guide surface. The first guide surface can be configured to contact the contact portion of the first layer and the second guide surface configured to contact the contact portion of the second layer.
The second guide can be positioned adjacent to the first guide surface. The second guide can have a complementary guide surface that is configured complementary to the first guide surface. The first guide surface and the complementary guide surface can be configured to sandwich the contact portion of the first layer.
In another embodiment, the first and second guides can be configured to contact and guide the first layer to cause an edge of the first layer to contact an edge of the second layer.
In another embodiment, both the first and second guides can be configured to contact and guide both the first and second layers to cause edges of the first and second layers to contact each other. The edges can be made to abut each other or slightly overlap. In this respect, the first guide can be configured to simultaneously heat both contact portions of the first and second layers. The heater can be configured to heat only the first guide to a temperature sufficient to melt the both contact portions. The second guide also can be configured to contact an outer side of the second layer and guide only the second layer.
In yet another embodiment, the first and second guides can be configured to contact and guide both the first and second layers to cause the first layer to overlap and contact the second layer. Here, the first guide can be configured to contact and simultaneously heat both contact portions of the first and second layers, and the heater can be configured to heat only the first guide to a temperature sufficient to melt the both contact portions.
The second guide can be configured to contact an outer side of the first layer and guide only the first layer. The second guide also can be configured complementary to the first guide surface so that the first and second guides sandwich the first layer.
The present apparatus can further include a pressing and cooling stage for at least cooling a fused seam.